What is the solution to this system of linear equations?

12q + 3r = 15

–4q – 4r = –44

12q + 3r = 15 . . . (1)
-4q - 4r = -44 . . . (2)

(2) x 3 => -12q - 12r = -132 . . . (3)

(1) + (3) => -9r = -117 => r = -117/-9 = 13
From (1), 12q + 3(13) = 15 => 12q + 39 = 15 => 12q = 15 - 39 = -24 => q = -24/12 = -2

q = -2, r = 13